Tuesday, January 29, 2013

Paper finds El Niño acts as a mediator of the solar influence on climate

A paper published in Paleoceanography finds another mechanism by which tiny changes in solar activity can cause greatly amplified effects upon the climate via the El Niño Southern Oscillation [ENSO]. According to the authors, the "east-west sea surface temperature gradient along the equator responds almost linearly to solar irradiance forcing [tiny changes in solar activity of 0.2 - 0.5%], with a short lag of about a decade," and "Overall, the sea surface temperature response is of the magnitude required, and is persistent enough, to induce important climatic perturbations worldwide. The results suggest that ENSO may plausibly have acted as a mediator between the Sun and the Earth's climate." In addition, the authors show that solar activity was at the highest levels of the past 10,000 years during the 20th century.

Using a climate model of intermediate complexity, we simulate the response of the El Niño–Southern Oscillation (ENSO) system to solar and orbital forcing over the Holocene. Solar forcing is reconstructed from radiocarbon production rate data, using various scaling factors to account for the conflicting estimates of solar irradiance variability. As estimates of the difference since the Maunder Minimum range from 0.05% to 0.5% of the solar “constant,” we consider these two extreme scenarios, along with the intermediate case of 0.2%. We show that for large or moderate forcings, the low-pass-filtered east-west sea surface temperature gradient along the equator responds almost linearly to irradiance forcing, with a short phase lag (about a decade). Wavelet analysis shows a statistically significant enhancement of the century-to-millennial-scale ENSO variability for even a moderate irradiance forcing. In contrast, the 0.05% case displays no such enhancement. Orbitally driven insolation forcing is found to produce a long-term increase of ENSO variability from the early Holocene onward, in accordance with previous findings. When both forcings are combined, the superposition is approximately linear in the strong scaling case. Overall, the sea surface temperature response is of the magnitude required, and is persistent enough, to induce important climatic perturbations worldwide. The results suggest that ENSO may plausibly have acted as a mediator between the Sun and the Earth's climate. A comparison to key Holocene climate records, from the Northern Hemisphere subtropics and midlatitudes, shows support for this hypothesis.

Amazing and extremely interesting. In essence I have used the seemingly minute changes of the Sun using one of L Svalgaards solar charts to "maybe" find an ENSO connection. But it always made sense to me and from early on that the heightened solar periods of the 20th century had to have a connection with the warming. If you go to my Wordpress page, then you can get a copy of the chart which Leif Svalgaard had posted last year, and which I have used to attempt to draw correlation with oceanic temp changes.